Here are some advices I share. Feel free to contribute:
1. Deck building
1.1. Power Points must be balanced. If you have too few cards in hand then your pp are low. If you have too many cards then your pp are high. My decks are a mathematically calculated distribution of 5/3/2 pps with very limited exceptions
1.2. Balance card types. 60% minions 30% spells 10% others are usually my stats
1.3. Design an opening. You have 3 pp at first turn. Make sure to have at least 2 card types which are good openings.
1.4 Decide your speed rate. Do you want to be quick or control the game? not both!
1.5. Keep strategy generic. Deck must be well balanced.
1.6. Don't mix strategies
1.7. Have a solution if the games goes in stall. 1 Card type must be dedicated to this.
2.1 Make your opening and try to destroy the one of the opponent
2.2. If a card you can play destroys more cards of the opponent DO IT
2.3. If the best card you have in hand cannot be destroyed PLAY IT
2.4. if the best card you have in hand can be destroyed then PLAY ANOTHER CARD FIRST to be sacrificed
2.5. Balance cards in hand properly. You should have in hand at least a big minion, a small minion and a spell. If you have more then play 2 cards. If you have less then use the extra power points to draw an extra card
2.6. Destroy key cards of the opponent
2.7. Keep alive your key cards
2.8. Remember that your goal is to damage the opponent and not minions. Do it unless opponent minions can become a problem
2.9. Remember that your goal is to set opponent life to 0. Nobody will care if you make him reach -20 for extra damages
3. Side game
3.1. Work on social tasks. Writing on this forum or on glassboard helps to know other players. They can share their skills with you
3.2. Play opponent decks. You'll learn how other strategies work. Even if you don't like them.
3.3. (If you have the skills to do it) do some math calculations when you compare cards in deck building. This will help on the long term.